GOD Replied,

"I AM WHO AM."

As he looked on, he was surprised to see that the bush, though on fire, was not consumed. So Moses decided, "I must go over to look at this remarkable sight, and see why the bush is not burned." Exodus 3:2-3

When the Lord saw him coming over to look at it more closely, GOD called out to him from the bush, "Moses! Moses!" He answered, "Here I am." GOD said, "Come no nearer! Remove the sandals from your feet, for the place where you stand is holy ground. I am the GOD of your father...the GOD of Abraham, the GOD of Isaac, the GOD of Jacob."... Exodus 3:4-6

"...What is His name? What Am I to tell them?"
GOD replied, "I AM Who AM." Then He added, "This is what you shall tell the Israelites: I AM sent me to you." Exodus 3:13-14